1. Field of the Invention
Exemplary embodiments of the present invention relate to a steering column for a vehicle, and more particularly, to a steering column for a vehicle capable of reducing driver's injuries by properly absorbing an impact caused in the event of a collision or rear-end accident of a vehicle.
2. Description of the Related Art
A steering system for a vehicle is a device which steers a vehicle for arbitrarily changing a forward direction of the vehicle. Such a steering system includes an operation mechanism, a gearing or a power cylinder, and a link mechanism, wherein the operation mechanism is configured by a steering wheel which is directly operated by a driver in order for the driver to change the forward direction of the vehicle, a steering shaft which is rotatably and integrally connected to the steering wheel to transfer torque of the steering wheel, a steering column which allows the steering shaft to be mounted to a vehicle body, and the like, the gearing reduces rotation of the steering shaft to increase operating force of the steering wheel and simultaneously changes a motion direction of the operation mechanism to transfer the same to the link mechanism, the power cylinder is hydraulically operated to assist a driver in operating the steering wheel, and the link mechanism is configured by a pitman arm, a drag arm, a knuckle arm, a tie rod, and the like in order to transfer operation of the gearing or power cylinder to front wheels while correctly supporting a relation position between left and right wheels.
In the event of a collision or rear-end accident of the vehicle to which the above-mentioned steering system is mounted, a driver's upper body directly strikes the steering wheel and the driver is seriously injured. Accordingly, in order to reduce such a driver's injury, there have been proposed a variety of buffer devices or buffer structures installed to the steering wheel, the steering column, or the like.
In addition, the conventional steering system has a tilt function by which the steering shaft may be tilted in forward and backward directions of the vehicle body by a predetermined angle in order to provide a more convenient operation environment of the steering wheel for a driver according to the body type thereof, a telescopic function by which the steering wheel may be pulled close to a driver's body or pushed downward to be away therefrom, or the like.
Here, in the steering system having only the tilt function, there has been proposed a buffer device or a buffer structure, such as a capsule which is installed to a part of the vehicle body equipped with the steering column so as to absorb an impact by being decoupled from the vehicle body when an impact more than a predetermined level is applied thereto, a press-fit friction structure in which a predetermined part of an outer tube fitted with an inner tube is cut and folded in the inner tube to be pressed against the inner tube so that an impact is absorbed by friction generated during relative movement between the tubes, or a molding pin which is installed to the steering shaft and absorbs an impact by being broken when the steering shaft is axially moved by an impact applied thereto.
Moreover, in the steering system simultaneously having the tilt function and the telescopic function, the above-mentioned molding pin cannot be used since a buffer device or a buffer structure has to be constituted such that an upper steering shaft and a lower steering shaft may be moved relative to each other. Accordingly, a buffer structure adopting the capsule which absorbs an impact by being decoupled from the vehicle body when an impact more than a predetermined level is applied thereto has generally been applied to the steering system. Here, the buffer structure to which the capsule is applied is disclosed in Korean Patent Publication No. 10-0798851.
Meanwhile, FIG. 1 shows an example of a steering system simultaneously having a tilt function and a telescopic function. FIG. 2 shows a component portion for tilt and telescopic functions. FIG. 3 shows a state of the component portion for tilt and telescopic functions shown in FIG. 2 when viewed from the bottom.
As shown in FIGS. 1 to 3, a steering column 10 in the steering system simultaneously having the conventional tilt function and telescopic function includes an outer tube 100 accommodating a steering shaft P, an inner tube 200 retracted into the outer tube 100, a main bracket 300 which is installed to the outer tube 100 and fixed to a vehicle body, a telescopic bracket 400 which is integrally fixed to the outer tube 100 and formed with a slot for telescoping 410, a tilt bracket 500 which is formed integrally with the main bracket 300 and formed with a slot for tilting 510, a position fixing bolt 600 installed through the slot for tilting 510 and the slot for telescoping 410, and an adjustment lever 700 which is joined to various gearings (not shown) installed to the tilt bracket 500 for the tilt and telescopic functions to control available and unavailable conditions of the tilt and telescopic functions.
In the configuration described above, when the adjustment lever 700 is pushed and the outer tube 100 is moved in a direction indicated by an arrow A for telescopic adjustment, the movement of the outer tube 100 is limited up to positions at which the position fixing bolt 600 is caught by both ends of the slot for telescoping 410.
However, in a case of the above-configured conventional steering system simultaneously having the tilt and telescopic functions, the component portion for tilt and telescopic functions is constituted independently from a component portion serving as a buffer function for the steering column during a vehicle impact. Therefore, since a large number of parts are used, there are problems in that assembly processes are complicated and manufacturing costs are increased.
In addition, the conventional buffer structure using the capsule instantly absorbs an impact load during the vehicle impact. Consequently, it may be impossible to efficiently realize impact absorption since times of action of an impact load may not be adapted in a multistage manner required to obtain a larger impact absorbing effect.